Home temperature, sleep loss tied to obesity

NEW YORK (Reuters Health) - Could we all help rein in the obesity epidemic by turning down our thermostats this winter? Maybe or maybe not -- but a new study suggests that environmental factors ranging from diet, to sleep to home temperature are related to the risk of becoming obese.

Junk food and physical inactivity usually catch most of the blame for the obesity problem weighing down much of the world.

But some recent research has been looking at the roles of the several other features of modern life -- like sleep deprivation and indoor climate control.

In the new study, published in the International Journal of Obesity, Dr. Simona Bo and colleagues at the University of Turin in Italy followed nearly 1,300 middle-aged adults over six years. During that time, 103 became obese.

When the researchers looked at a number of environmental factors, they found that sleep habits were related to the risk of becoming obese. For each hour of sleep people typically got each day, the odds of their becoming obese declined by 30 percent -- even with other factors like physical activity level and TV watching taken into account.

Then there was home temperature. Compared to people who kept their homes no warmer than 20 degrees Celsius (68 degrees Fahrenheit) in the fall and winter, those who liked a toastier home were twice as likely to become obese.

Diet, a more obvious factor in obesity, also mattered: the more often people ate at restaurants each week, the greater their likelihood of becoming obese. And those who got little fiber in their diets were at greater risk of developing abnormally high blood sugar levels, often a sign of type 2 diabetes.

None of this proves that turning down the heat or sleeping more will make you thin.

"I wouldn't say to anyone that if you turn down your thermostat, you'll lose weight," said Dr. David B. Allison, director of the Nutrition Obesity Research Center at the University of Alabama at Birmingham.

On the other hand, things like home temperature and sleep habits are lifestyle factors that "you can play with" in managing your weight, according to Allison, who was not involved in the current study.

"It is plausible that if you turn down your thermostat in the winter, or use less air conditioning in the summer, you'll lose weight," Allison told Reuters Health. "And you'll almost certainly reduce your energy bills."

Why would indoor temperature matter? According to Allison, it's fairly simple: the body burns more calories when it has to work to maintain a stable temperature. This is true in both hot and cold weather, he notes.

To best of his knowledge, Allison said, this latest study is the first to connect home-temperatures with individuals' risk of becoming obese.

As for sleep, a number of past studies have linked excess weight and chronic sleep deprivation -- typically defined as less than six hours per night. One theory is that the hormonal effects of sleep loss are to blame. Another is that sleep-deprived people may eat and drink more in an effort to boost their energy levels.

So does any of this mean that you can just forget exercise if you pay more attention to your thermostat? No.

Allison said there is "little doubt" that if you work out regularly -- and do not replace those burned calories by eating more -- you will lose weight.

The problem has been getting people to actually do that. Programs and public-health efforts to get Americans moving -- like more physical education in schools -- have so far met with little success when it comes to the nation's obesity problem, according to Allison.

"I think we need to explore alternative ideas," he said.

In a 2006 study of air conditioning and obesity rates, Allison and his colleagues cited a number of modern-life factors they say could be contributing to rising obesity -- including widespread use of antidepressants and other medications that can promote weight gain, and industrial chemicals that may alter hormone activity when they get into the body.

Researchers and public-health advocates should be "open-minded" about the possible contributors to obesity, he added, rather than fixating on one thing, like physical education at schools.